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Multi-Way Conventional loudspeakers with crossovers

Rebuilding The Great Technics SB-X50
Rebuilding The Great Technics SB-X50
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Old 9th July 2014, 11:05 PM   #1
Einric is offline Einric  United States
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Rebuilding The Great Technics SB-X50
Default Rebuilding The Great Technics SB-X50

I am fortunate enough to have a HiFi father that is a bit of a hoarder.
On a recent trip home for the 4th of July my father agreed to let me take ONE pair of his Technics SB-X50's home with me.
He purchased them new while he was on a trip to Japan in 1976.
They are rated at 93db sensitive and I would tend to agree with this rating based upon my initial low power tests.
They have a 1" soft dome, 3.5" paper mid with inverted neoprene surround and a 10" paper woofer with inverted cloth surround.
The surrounds on all of the drivers are still in very good shape.
The rubber parts even still have that bit of white powder that new rubber has on it.
The factory crossover points are 1000hz and 3000hz.
As is they really sound very good even for being 40 years old with dried up electrolytic caps.
They image VERY well and I can hear things all around the room from directly in front and out to the sides even slightly above and below.
The drivers are physically time aligned and the speakers were marketed as Linear Phase design.
I will be going through them and replacing the old electrolytic capacitors with Met-Poly except for the 330uF in the midrange tank (that will be a mix).
They are in near pristine condition and have a very slight grunge in the sound which is the reason I will be replacing the capacitors in the crossovers.

In this thread I will chronicle my progress and field any questions along the way.
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File Type: jpg SB-X5 Crossover.jpg (466.9 KB, 413 views)
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Old 10th July 2014, 01:16 AM   #2
oldmanaudio is offline oldmanaudio  United States
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Looks like a fun project. Have you thought of trying to design your own crossover?
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Old 10th July 2014, 01:27 AM   #3
Einric is offline Einric  United States
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Rebuilding The Great Technics SB-X50
No Way, this crossover looks very well thought out even compared to the modern designs and ideas.
I bet the engineers at Panasonic had their thinking caps on when they designed these.
Somewhere my father has all of the original documentation including impulse and phase response graphs.
From some of the scans I have seen on the internet of this documentation there would be NO WAY I could even come close to designing something comparable myself.

I have however already thought about changing the vinyl walnut veneer for real walnut veneer.
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Old 10th July 2014, 03:40 AM   #4
Inductor is offline Inductor  Portugal
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The crossover electric transfer would be similar to this, notice the inversion of phase on the tweeter (OP) working with horn loading.
In case someone wants to use other drivers, Visatons, SSs or others.
Technics SB-X50 on thevintageknob.org
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File Type: jpg 3-way Technics SB-X50.jpg (160.1 KB, 334 views)
File Type: jpg 3-way Technics SB-X50 section.jpg (119.4 KB, 358 views)
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Old 10th July 2014, 03:56 AM   #5
6L6 is offline 6L6  United States
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Rebuilding The Great Technics SB-X50
What a great project!

I wish I could come up and hear them before and after...
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Old 10th July 2014, 04:29 AM   #6
Einric is offline Einric  United States
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Rebuilding The Great Technics SB-X50
Anybody around Bozeman is welcome to stop by for a listen.
I will be picking up the bulk of my caps from ApexJR.
He is out of town for a few days so there will be a slight delay.
Tomorrow I will pull one of the woofers and get a look at the crossover.
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Old 10th July 2014, 05:54 AM   #7
picowallspeaker is offline picowallspeaker  Italy
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Well, Inductor pointed to the VKnob site, and it says. "Thermal relays for each drivers are placed at the input point of the speaker coils set in as soon as excessive heat builds up caused by amplifier clipping ; the reset buttons are located at the back, just above the terminals."
I would skip those !
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Old 10th July 2014, 12:27 PM   #8
Einric is offline Einric  United States
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Rebuilding The Great Technics SB-X50
I have children in the house so I think it would be wise to leave the driver protection in place for now.
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Old 10th July 2014, 12:46 PM   #9
picowallspeaker is offline picowallspeaker  Italy
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Sort of microchips under the skin ?
When children are around, it activates a "-20 dB" relay so the amp won't clip
anytime

Or maybe a hidden gain control.
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Old 10th July 2014, 12:49 PM   #10
afa is offline afa  Australia
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They look very similar to Bang & Olufsens Linear phase designs of the same vintage.
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